Fixes for #170

Sorry for the messy commit. We had made several changes in our internal fork of this project and I did my best to revert those for this pull request.

These changes allow rubycas-server to follow redirects given by the client app while obtaining a PGT. We follow up to 10 redirects. I added some additional debug logging as well.

There is a new optional config item `validate_ssl`. It defaults to true. This allows rubycas-server to be stood up in dev much easier.